Conventionally, an indicator for a vehicle that indicates a vehicle condition value according to a rotation position of a pointer is well known. A driving signal is applied to a field winding of a step motor so that the pointer is rotated. The driving signal is alternately oscillated according to an electric angle. In this indicator, the pointer rotates toward a zero point returning direction so that the pointer returns to a zero point position, which shows a zero value of the vehicle condition value.
In an indicator for a vehicle described in JP-A-H06-38593, a pointer rotates toward a zero point return direction that shows zero value of a vehicle condition so that the pointer returns to the zero point. A driving signal is applied to a field winding of a step motor, and is controlled to rotate the pointer toward the zero point return direction by a zero point angle of an electric angle corresponding to a scale angle equal to or larger than a maximum scale angle. Then, a stopper system stops the pointer at a stopper position, which is disposed in a predetermined range from the zero point toward the zero point return direction. Specifically, in this case, a zero point stopper position detection with zero point return enforcement function is executed. Here, the electric angle corresponding to the stopper position is defined as a reference angle of driving signal control.
In an indicator for a vehicle described in JP-B2-3770095 corresponding to US 2002/0117988, a driving signal is applied to a field winding of a step motor and is controlled to rotate a pointer toward a zero point return direction. In this case, an induced voltage generated in the field winding is detected thus, when the pointer is rotating, the induced voltage is generated in the field winding. When the pointer stops rotating, the induced voltage in the field winding is reduced. Thus, when the detected induced voltage in the field winding is equal to or smaller than a predetermined value, the indicator estimates that the pointer stops at the stopper position. Specifically, a voltage type zero point stopper position detection is executed. An electric angle corresponding to the stopper position is updated and registered. In this process, it is possible to control the driving signal accurately according to the updated and registered electric angle even if the step motor malfunctions because of external disturbance such as vibration so that the rotation position of the pointer is shifted from a certain position before the indicator starts to function.
A meter system includes an indicator for a vehicle, a turn lamp or a hazard lamp, a buzzer and a flasher device for controlling a lamp to turn on and off and for controlling a buzzer to outputting sound in conjunction with the lamp. Here, the turn lamp, the hazard lamp the buzzer and the flasher device may generate a noise. The noise generates magnetic field, which influences the field winding. Recently, the flasher device is integrated with the indicator so that the indicator has a flasher function. Thus, the meter system is much integrated, and a manufacturing cost is reduced.
However, when the indicator has the flasher function, it is necessary to arranged a flasher semiconductor switch around the field winding of the indicator. The flasher semiconductor switch turns on and off the flasher device. Further, the switch turns on and off when the flasher device switches on and off. An inductive noise may be generated when the switch turns on and off.
Accordingly, when the semiconductor switch of a flasher function unit functions while the voltage type zero point stopper position detection is executed, detection error of the stopper position may occur because of the inductive noise. Thus, the stopper position may shift, and therefore, the indicator does not show a correct value of the vehicle condition value. Specifically, even if the pointer does not contact the stopper, the system mistakes to determine that the pointer contacts and stops at the stopper. Alternatively, even if the pointer contacts and stops at the stopper, the system mistakes to determine that the pointer rotates. In these cases, the pointer does not indicate the correct vehicle condition value.
On the other hand, even when the semiconductor switch of the flasher function unit functions while the zero point stopper position detection with zero point return enforcement function is executed, the detection error of the stopper position caused by the inductive noise is not generated, and the stopper position does not shift. However, in the zero point stopper position detection with zero point return enforcement function, loss of synchronism and zero point return operation are alternately repeated under a condition that the pointer stops at the stopper position. Thus, the pointer may vibrate. In this case, visual quality of the meter system is not good, and or abnormal noise may be generated. Thus, a user may feel strangeness, so that the user may consider that the meter system is broken.
Further, it is necessary to satisfy a predetermined stopper position detection operation executing condition when the stopper position detection operation is executed. The stopper position detection operation executing condition includes a high necessity executing condition and a confirmation executing condition. The high necessity executing condition provides high necessity for executing the stopper position detection operation rapidly since a possibility that the pointer is spaced apart from the stopper position is high. The confirmation executing condition provides necessity for executing the stopper position detection operation in order to confirm the zero point although a possibility that the pointer is spaced apart from the stopper position is low. When the high necessity executing condition is satisfied, the necessity for executing the stopper position detection operation is high. When the confirmation executing condition is satisfied, the necessity for executing the stopper position detection operation is not high. When the stopper position detection operation is executed, the vehicle condition value is indicated with high accuracy. However, the user may feel strangeness since the pointer rotates toward the zero point returning direction although the user does not operate the meter system.
Further, in view of the above difficulty, it is considered that the stopper position detection operation is executed in priority to the flasher function. However, the user merely recognizes the operation of the flasher when the flasher blinks. Accordingly, when the user operates the combination lever or when the user switches the hazard lamp on, if the blink of the flasher is delayed, the user may misunderstand that the flasher is broken.